In many of Africa’s waterways lives one of the heaviest animals on earth. Their closest living relatives are cetaceans - the whales and dolphins. Despite fearsome tusks and a jaw that can open wider than any other land mammal, they are herbivores.The ancient Greeks named the animal ‘River Horse’. We call it the Hippopotamus. In Zambia’s Luangwa River, hippos dominate life in the water – here they reign supreme.